There are even some significant changed in George Martin's Game of Thrones from the books and he's still alive. They don't even show Reaghar's son who's still alive and is supposed to be gathering his armies to take Westeros. Although, if Jon Sno really is Rheagar's and Lyanna Stark's son they might be working that angle instead of Danny and her other nephew.

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"For believe me: the secret for harvesting from existence the greatest fruitfulness and the greatest enjoyment is - to live dangerously!" - G.S.; F. Nietzsche